1. Field of the Invention
The present invention relates to a steering column device provided with a jacket supporting a steering shaft rotatably.
2. Description of the Related Art
Published Japanese Translation of PCT International Publication No. 2005-506245, Japanese Unexamined Patent Application Publication No. Hei 10-157634, and European Patent Application Publication No. 0849141 disclose steering column devices of the related art, each of which includes a jacket supporting a steering shaft rotatably, a jacket guide configured to guide the jacket, and a lock mechanism configured to lock the jacket by tightening a clamp bolt.
As shown in FIG. 1, a steering column device 100 disclosed in Published Japanese Translation of PCT International Publication No. 2005-506245 includes a steering shaft 101 having an upper shaft 101a with an upper end in an axial direction to which a steering wheel (not shown) is to be fixed, and a lower shaft 101b fitted in the upper shaft 101a, a jacket 102 supporting the steering shaft 101 rotatably, a jacket bracket 103 fitted on the jacket 102, a jacket guide 104 disposed between the jacket bracket 103 and a mount bracket 107 and configured to guide the jacket bracket 103, and a lock mechanism 106 configured to fasten and fix the jacket bracket 103 and the jacket guide 104 to the mount bracket 107 by tightening a clamp bolt 105. A toothed rail member 109 is connected to the jacket bracket 103 by use of an energy absorbing device 108. The clamp bolt 105 supports a toothed member 110 which is provided on one end close to the jacket 102.
In the above-described configuration, when an unillustrated operating lever is rotated in a locking direction, the clamp bolt 105 is pulled downward in FIG. 1 by an action of the lock mechanism 106, whereby the jacket bracket 103 and the jacket guide 104 come into close and pressure contact with each other while the toothed member 110 is engaged with the toothed rail member 109. Accordingly, the jacket bracket 103 is locked to the jacket guide 104 in a telescopic direction. Meanwhile, the jacket guide 104 comes into pressure contact with the mount bracket 107 and is thereby locked in a tilt direction. Subsequently, when the operating lever is rotated in an unlocking direction, the state of pressure contact between the jacket bracket 103 and the jacket guide 104 is released through the clamp bolt 105 by an unlocking action of the lock mechanism 106, thereby releasing the locked state of the jacket bracket 103 with the jacket guide 104. Similarly, the state of pressure contact between the jacket guide 104 and the mount bracket 107 is also released, thereby releasing the locked state of the jacket guide 104 with the mount bracket 107. At the same time, the toothed member 110 is released from the state of engagement with the toothed rail member 109 and is biased by an unillustrated leaf spring in a direction away from the toothed rail member 109. In this way, it is possible to adjust a tilt position and a telescopic position of the steering shaft 101.
As shown in FIG. 2, a steering column device 120 disclosed in Japanese Unexamined Patent Application Publication No. Hei 10-157634 includes a steering shaft 121 with an upper end in an axial direction to which a steering wheel (not shown) is to be fixed, a jacket 122 supporting the steering shaft 121 rotatably, a guide member 123 configured to guide the jacket 122, and a lock mechanism 124 configured to lock the jacket 122 to the guide member 123. The lock mechanism 124 mainly includes paired gear portions 125 and 126 provided inside the jacket 122, a clamp member 128 provided with a bolt 127 having a head 127a coupled with the movable gear tooth portion 126 out of these gear tooth portions, and an operating lever 129 configured to move the clamp member 128. The bolt 127 is provided with a constricted part 127b located between the jacket 122 and the guide member 123.
In the above-described configuration, when the operating lever 129 is rotated in an unlocking direction, the bolt 127 moves toward the steering shaft 121 to release a state of engagement between the paired gear tooth portions 125 and 126 (shown disengaged). This release allows the jacket 122 to move in an axial direction. Meanwhile, when the operating lever 129 is rotated in a locking direction, the bolt 127 moves in a direction away from the steering shaft 121 and the paired gear tooth portions 125 and 126 are engaged with each other (shown disengaged). The engagement locks the jacket 122 to the guide member 123 and does not allow the jacket 122 to move in the axial direction. At this time, if an excessive impact in the axial direction larger than a predetermined value is applied to the jacket 122 via the steering shaft 121 by a driver bumping into the steering wheel due to a vehicle crash, for example, the bolt 127 receives a shearing force and breaks at the constricted part 127b. At this time, the head 127a of the bolt 127 breaks off to release the state of engagement between the paired tooth portions 125 and 126. This release allows, the jacket 122 to move in the axial direction and the steering shaft 121 contracts and absorbs the impact energy.
As shown in FIG. 3, a steering column device 130 disclosed in European Patent Application Publication No. 0849141 includes a mount bracket 132 having an elongated hole 131 extending in a tilt direction, a lock mechanism 134 configured to lock a jacket 133 to the mount bracket 132, and a block 137 located between the mount bracket 132 and an operating lever 135 of the lock mechanism 134 and provided with a round hole (not shown) into which a clamp bolt 136 is inserted. Here, paired gear tooth portions 138 and 139 to be engaged with each other are formed on the mount bracket 132 and on the block 137, respectively.
In the above-described configuration, when an operating lever 135 is rotated in a locking direction, the jacket 133 is pulled toward the mount bracket 132 by the clamp bolt 136 of the lock mechanism 134, whereby the movable gear tooth portion 139 on the block 137 is engaged with the fixed gear tooth portion 138 on the mount bracket 132 to lock the jacket 133 to the mount bracket 132. Subsequently, when the operating lever 135 is rotated in an unlocking direction, the pulled state of the clamp bolt 136 is released by the lock mechanism 134, whereby the clamp bolt 136 is allowed to move toward the jacket 133 to release the locked state of the jacket 133 to the mount bracket 132.